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cse2331-lec10

# We could use a sorted array to do all these in o1

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Unformatted text preview: 31/5331 Tree-Insert(T, z) n Insert z into tree T, and resulting tree still binary search tree 15 6 3 2 18 7 17 20 13 4 Tree-Insert(T, 8) Use Tree-search ! 9 CSE 780 Algorithms Pseudocode n Tree-insert(T, z) y = Nil, x = root[T] while (x ≠ Nil) do y=x Locate potential parent y of z. if ( z.key < x.key ) then x = x.left else x = x.right z.parent = y if (y = Nil) then root[T] = z Time: O(h) else if (z.key < y.key) then y.left = z else y.right = z CSE 780 Algorithms Build Binary Search Tree CSE 780 Algorithms Deletion 15 6 3 2 18 7 17 13 4 9 20 16 23 delete 17?? delete15 6 3 7 4 CSE 780 Algorithms Three Cases for Deleting z n n Case 1: Leaf node Case 2: Has only one child n n Replace z with its child Case 3: Has both children n Find its successor y n n n y cannot have left child! replacing y with its right child! Replace z with y The “replacement’’ is implemented by the transplant operation CSE 780 Algorithms Transplant Operation CSE 2331/5331 Case 3: More Detailed View n n n Goal: delete node z Let y be the successor of z Case-(3.1) n n y is the right child of z Then replace z by y CSE 2331/5331 Case 3: cont. n Case (3.b): n n y is not the right child of z First replace y by its own right child, and then replace z b y y. CSE 2331/5331 Delete together cover Cases 1 & 2. Time complexity: O(h) CSE 2331/5331 An Exercise Delete I ? Delete G ? Delete K ? Delete B ? CSE 2331/5331 Remarks n n n All complexity depends on height h h = (lg n), h = (n) To guarantee performance: n n Balanced tree ! Randomly build a tree n n Expected height is O(lg n) Still problem: future insertions … CSE 780 Algorithms...
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